Oxytrifluoromethylation of multiple bonds using copper catalyst under mild conditions

Oxytrifluoromethylation reaction of styrene derivatives and alkynes with external and internal oxygen nucleophiles, catalyzed by copper (I) salts under mild conditions, was developed. Direct formation of a β-trifluoromethylstyrene derivative from a styrene derivative was also achieved by the reaction in the presence of a Brønsted acid. Further transformation of the oxytrifluoromethylated products was conducted to demonstrate their utility.     

Pd-catalyzed selective addition of heteroaromatic C-H bonds to C-C triple bonds under mild conditions

Simple heteroarenes such as pyrroles and indoles undergo addition reactions to C-C triple bonds in the presence of a catalytic amount of Pd(OAc)(2) under very mild conditions, affording cis-heteroarylalkenes in most cases. The cleavage of aromatic C-H bonds is the possible rate-determining step in CH(2)Cl(2), and the addition of heteroaromatic C-H bonds to C-C triple bonds is in a trans-fashion.     

A magnetic biomimetic nanocatalyst for cleaving phosphoester and carboxylic ester bonds under mild conditions

[Structure: see text] As a result of the unique surface structure of nanospheres, Asp and His residues supported on a 12 nm maghemite nanoparticle worked collaboratively as a biomimetic nanocatalyst for hydrolyzing paraoxon (phosphoester) and 4-nitrophenyl acetate (carboxylic ester) in Milli-Q water (pH 7.0) at 37 degrees C, without employing extremes of pH or heavy metals. Our nanocatalyst could be facilely recovered via magnetic concentration. The isolated catalyst exhibited long-term stability, showing no significant loss of its catalytic activity for repeated uses after 3 months.     

Straightforward microwave-assisted synthesis of 2-thiazolines using Lawesson's reagent under solvent-free conditions

2-Thiazolines are synthesized from carboxylic acids and 1,2-aminoalcohols in the presence of Lawesson's reagent under solventless conditions. The developed method is valid for either substituted or unsubstituted aminoalcohols and a wide variety of aromatic, heteroaromatic and aliphatic carboxylic acids; thus it constitutes a general synthetic method for these kinds of compounds. The role of Lawesson's reagent is dual: to transform the 1,2-aminoalcohol into 1,2-aminothiol and to activate its reaction with the carboxylic acid leading to the formation of a thiazoline ring, all in one pot.     

Formation of a cyclobutylidene ring: intramolecular [2 + 2] cycloaddition of allyl and vinylidene C=C bonds under mild conditions

Intramolecular [2 + 2] cycloaddition of two C=C bonds in vinylidene complexes [Ru(eta5-C9H7){=C=C(R)H}(PPh3){kappa1-(P)-PPh2(C3H5)][BF4] affords cyclobutylidene complexes [Ru(eta5-C9H7){kappa2-(P,C)-(=CC(R)HCH2CHCH2PPh2)}(PPh3)][BF4], which can be also obtained by reaction of terminal alkynes with [Ru(eta5-C9H7)(PPh3){kappa3-(P,C,C)-PPh2(C3H5)}][PF6]. The reaction proceeds under mild conditions via vinylidene complexes, and the activation parameters were determined by kinetic studies.     

Regeneration of carbonyl compounds by cleavage of CN bonds under mild and completely heterogeneous conditions

Oximes, hydrazones, semicarbazones and azines are converted to the corresponding carbonyl compounds using a combination of Zr(HSO₄)₄ and wet SiO₂ in good to high yields under completely heterogeneous conditions.     

Efficient functionalization of aromatic C-H bonds catalyzed by gold(III) under mild and solvent-free conditions

A gold(III)-catalyzed carbon-carbon bond formation reaction between arenes and electron-deficient alkynes or alkenes is described. Electron-rich arenes can be efficiently functionalized with the alkyne or alkene substrates. This reaction can be run with neat reactants at ambient temperature. Under the "solventless" conditions, clean product was obtained from a reaction of equal molar amounts of arene and alkyne substrates. The mild conditions and potential tolerance to different functional groups make this method practical for arene functionalization and for constructing complicated molecules. Efficient preparation of various coumarins from aryl alkynoates was demonstrated. Preliminary mechanistic studies were performed to probe the pathway of this reaction.     

Electrostatic and covalent contributions in the coordination bonds of transition metal complexes

To develop a molecular mechanics force field for modeling complexes of transition metals and organic ligands, the electrostatic and covalent contributions in the coordination bonds were investigated using quantum mechanical density functional theory and model complexes of glyoxal diimine and the 2+ cations of the first row transition metals. The VDD and Hirshfeld charges are found to be closely correlated with the extent of the electron transfer between the ligands and the cations. Assuming the electrostatic contribution can be represented by the atomic partial charges, the covalent contributions in the coordination bonds are estimated to be in a range of 54-92% for the systems calculated. A simple force field was parametrized to validate the partial charge representation.     

温和条件下稀土氯化物-萘催化的碱金属氢化物的合成

本文研究了稀土氯化物对碱金属氢化反应的催化作用。金属钠在稀土氯化物LnCl~3(Ln=La,Nd,Sm,Dy,Yb)和萘的催化下,在常压、40℃下能与氢气反应,生成氢化钠;稀土氯化物的催化活性顺序为LaCl~3>NdCl~3>SmCl~3>DyCl~3>YbCl~3。金属锂可发生类似反应,生成LiH;但其反应动力学曲线与金属钠相比明显不同。稀土氯化物对金属钾的氢化反应不显示催化作用。对反应机理的初步探索表明:碱金属与萘反应生成的阴离子自由基型物种可能是氢化反应的中间体,稀土氯化物的作用是催化该中间体的氢化反应。该反应的产物是一类大比表面积(NaH的比表面积为83m^2/g)、多孔性固体粉末,在空气中可自燃。它们具有比一般市售碱金属氢化物高得多的反应活性,并能与过渡金属配合物组成高活性烯烃加氢催化。     

Formation of the imidazolinone ring under mild conditions in the presence of sodium hydride

Substituted imidazolinones containing heterocyclic carboxylic acids as substituents and possessing herbicidal properties were synthesized by cyclization of 2-amino-2,3-dimethylbutyramide with heterocyclic ethyl dicarboxylates under mild conditions. The use of NaH as base leads to a significant increase in the reaction rate and allows the preparation of the target compounds in high yields.     

Efficient metalloporphyrin synthesis under mild conditions using N-benzylporphyrins.

A general method has been developed for nearly quantitative synthesis of N-benzylporphyrins by use of benzyldiphenylsulfonium tetrafluoroborate. The N-benzylporphyrins (including natural, synthetic, water soluble and non-water soluble porphyrins) insert Cu(II), Co(II), Pd(II) and Ni(II) rapidly and then readily lose the N-benzyl group to give non-N-substituted metalloporphyrins. The reactions of Cu(II), Co(II) and Pd(II) are efficient under mild conditions compatible with biological preparations.     

Aryl ether as a Negishi coupling partner: an approach for constructing C-C bonds under mild conditions

An etheric Negishi coupling: The first cross-coupling reaction between aryl alkyl ethers and dianion-type zincate reagents to afford biaryl compounds through selective cleavage of the etheric C(sp(2))-O bond was developed. Dianion-type zincates showed excellent reactivity toward the aromatic ethers under mild conditions, with good functional group compatibility (see scheme).     

Rearrangement of indene skeletons under mild conditions

Isomerization between two isomers of 1,2-disubstituted 3-aminoindenes occurs via the rearrangement of indene frameworks. In contrast to previous rearrangements of indene derivatives, which occur under high-temperature conditions or the irradiation of light, this rearrangement proceeds at room temperature without UV light irradiation. An amino group at the 3-position plays an important role to accelerate the rearrangement under mild conditions.     

Synthesis of tetraphenylporphyrins under very mild conditions

Reaction of pyrrole and an aromatic aldehyde at room temperature affords the corresponding tetraarylporphyrinogen in high yield at thermodynamic equilibrium. Oxidation yields the porphyrin. The reaction conditions are of broad scope.     

Efficient difluoromethylation of isoflavonoids and flavonoid under mild conditions

A simple and efficient protocol for difluoromethylation of isoflavones, flavonoids, and coumarins has been developed. The protocol uses readily available, non-ozone-depleting and easy handling BrCF₂PO(OEt)₂ as difluorocarbene precursor. The reaction underwent the formation of difluorocarbene under mild reaction conditions with relatively weak base therefore demonstrates high selectivity. Application of the reaction led to difluoromethylated biologically relevant molecules.